Autonomous Underwater Vehicles (AUVs) have seen rapidly expanding usage over the past decade with advances in computation, miniaturization, sensors, and energy storage. Modern AUVs are able to explore the deepest depths of the world's oceans and collect a wide assortment of useful information for commercial, military, and scientific missions. These AUVs are however limited in endurance due to the restricted energy storage capacities of current battery technology. With these limitations, typical AUV endurance is approximately one day with a manual retrieval and recharging process required between missions. The manual retrieval and recharging process necessitates a manned surface vessel to support the AUV, dramatically increasing costs. In open ocean, manned surface vessel costs are in excess of $30,000 USD/day. Despite the large costs, extended AUV missions do occur such as mine detection, Arctic studies and marine geoscience.
One proposed solution to the endurance limitation of AUVs is automated underwater charging stations. These charging stations can be equipped with sources of power either through renewables (solar, wind, wave) or shore power, meaning that they can support charging AUVs indefinitely. Using existing technology, some AUVs are able to operate for extended periods away from manned surface vessels. These existing stations however are limited in their adaptability to other platforms, are costly to install, and are unable to be modified for mobile applications. Additionally, the infrastructure to support persistence is fixed which is not suitable for transient or expansive missions.
Docking stations for autonomous underwater vehicles traditionally belong to one of two types: a large cone-shaped funnel or a pole. By far the most common docking technique is the cone-shaped funnel. In this style of docking station, a large funnel is installed on either the seafloor or any other large system such as on a much larger AUV. The docking procedure for funnel designs involves the AUV homing into the funnel and being guided in by bouncing off of and sliding along the funnel face. Once inside of the funnel, the AUV is latched and power transfer is begun. To undock, the AUV uses reverse thrust until a safe distance away before resuming the mission. Funnel based designs have an excellent capture envelope due to the nature of the funnel shape. They are, however, bulky systems to install and are not adaptable to support multiple types of AUVs.
Pole type docking systems involve a fixed vertical pole with a flat V-shaped latching mechanism on the nose of the AUV. Once latched, the AUV is pushed into the docked position through motorized carriages on the docking station. Pole-based designs enable a large vertical capture area with a relatively small horizontal capture area. Pole docks have historically had problems with homing and maintaining the necessary vertical attitude.
More novel docking solutions have been experimented with including grappling type, stinger and puck, hook, and vertical cones. All of these various solutions each have unique benefits and drawbacks. For example, large funnel shaped docks have a large capture envelope however, the excessive size is a drawback. The small size of the grappling type is desirable, but the capture envelope is very small. An additional consideration in the marine environment (as compared to docking of aerial or space vehicles) is biofouling.